Pediatric obsessive compulsive disorder is common and associated with significant functional impairment. Even with the treatment of choice for this disorder, cognitive behavior therapy (CBT), up to 60% of youth do not experience clinical remission of symptoms1, suggesting there is a need for improvement in the treatment of pediatric OCD. However, mechanisms of CBT are poorly understood and therefore it is not clear how to maximize the mechanisms involved. One proposed mechanism is strategic approach of feared situations through completion of exposure exercises. Thus one strategy for treatment improvement may involve maximizing the number of exposures completed. However, evidence suggests that CBT also modifies automatic approach of feared situations. Furthermore, automatic approach may be manipulated more efficiently than strategic approach through approach-avoidance training (AAT), a computerized task designed to facilitate automatic approach towards OCD-relevant stimuli. Thus, change in automatic approach bias is another candidate mechanism of CBT. Moreover, automatic approach mechanisms are easily mapped onto underlying neurobiological markers, such as the N2 event-related potential component recorded during electroencephalography (EEG). In the current proposal, we aim to compare the relative contributions of changes in (a) automatic and (b) strategic behavioral approach in predicting symptom change. We will manipulate automatic approach through AAT training, and strategic behavioral approach through exposure exercises completed in the context of a brief-family based CBT program (BF-CBT). Participants will be encouraged to complete as many exposures as possible during the course of treatment. Moreover, we will measure neurobiological markers of AAT (i.e., N2). We plan to assign 25 children ages 8-12 with a primary diagnosis of OCD to eight weeks of BF-CBT plus AAT training. We will preliminarily test and estimate effect size for the hypothesis that automatic approach (i.e., change in approach bias) will predict symptom change above and beyond the effect of strategic approach (i.e., number of exposure exercises completed). Furthermore, we will preliminarily test and estimate effect size for the hypothesis that the relationship between change in automatic approach bias and reduction in symptoms will be mediated by decreases in N2 from pre- to post-treatment. The knowledge gained from this proposal will increase understanding of both behavioral and neurobiological mechanisms of treatment response in pediatric OCD, and may yield insights regarding specific mechanisms to be more effectively targeted in future treatment efforts.